Trinethylamine (TMA) is an offensively smelling gas having an irritating, fishy and ammonia-like odor, and is a listed substance under restriction control according to the regulations on the air pollution control act. With respect to the quality control in food industry, the amount of volatile alkali substance such as trimethylanine will increase during the putrefaction of seafood (e.g. fish and shrimp). Therefore, the level of putrefaction of seafood can be indicated by the detection of the amount of trimethylamine present (Nonaka, J. et al., Bull. Japan Soc. Sci. Fish, Vol. 58, pp. 2039-2044, 1967). With respect to medical diagnosis, an increase of concentration of trimethylamine in the breath of patients can be used as an index of virernic diseases. (Siminhoff, M. L. et al., N. Engl. J. Med. Vol. 297, pp. 132-135, 1977). Therefore, the techniques for detecting trimethylamine are applicable in the fields of environmental protection, food industry and medical diagnosis.
In general, trimethylamine is determined by, for instance, acid titration and instrumental analysis such as gas chromatography, and mass spectrometry. However, such methods have some disadvantages, such as which involve complicated operation procedures, and are time-costing and difficult to analysis.
In view of the fact that various odorant molecules are identified by olfactory organs due to the binding of the odorant molecules and the receptor proteins on olfactory cilia (ancet D., Annu. Rev. Neurosci, Vol. 9, pp. 227-255, 1986). In 1991, the gene family of the olfactory receptor proteins were cloned and characterized. The protein sequences of the odorant receptors were determined by Buck and Axel (Buck, L. and Axel, R, Cell Vol. 65, pp. 175-187, 1991). In addition, a device for identifying the aroma of the wine through the binding by an olfactory receptor protein of a bullfrog was published (Wu, T. Z., and Wan, H. H., Analytical Science Vol. 7, Supplement, pp.867-870, 1991).